Two journalists arrested in connection with the alleged theft of confidential material used in a documentary on the Loughinisland massacre have been released.

Award-winning reporters Trevor Birney, 51, and Barry McCaffrey, 48, were detained for questioning over material used in their film on the 1994 shootings in the Co Down village.

They walked out of Musgrave Street police station in Belfast at 8.55pm having been arrested at 7am on Friday morning.

Their solicitors said the men had been released on bail.

Six men were murdered when loyalists opened fire on a crowd of football fans gathered around a TV in a pub in Loughinisland watching the Republic of Ireland play in the World Cup.

Undated family handout photo of (top row left to right) Patsy O'Hare, Barney Green, Adrian Rogan, (bottom row left to right) Eamon Byrne, Daniel McCreanor and Malcom Jenkinson, who were killed in the tiny Heights Bar in Loughinisland, Co Down by UVF gunmen while they were watching Republic of Ireland playing Italy in their USA 94 World Cup group match (Image: Loughinisland/PA Wire)

Last year's No Stone Unturned documentary examined the persistent claims of state collusion in the murders and broke new ground by publicly naming what it said were suspects.

Police said the confidential material under investigation had been in the possession of the Police Ombudsman for Northern Ireland (PONI).

A police spokesman has claimed the theft of the documents "potentially puts lives at risk".

PONI officers reported the alleged theft to the Police Service of Northern Ireland (PSNI).

The PSNI then asked Durham Police to conduct an independent investigation into the claims.

Flanking his client outside the police station, Mr McCaffrey's lawyer John Finucane said he was "deeply disturbed" by the men's detention.

"What I have witnessed today is nothing more than a very sinister attack on the freedom of the press," he said.

Mr Birney's solicitor Niall Murphy said his client had gone through four taped interviews in custody.

"Throughout those interviews not one scintilla of evidence was put to Mr Birney," he said.

"It was very apparent at all times that the PSNI's predominant interest was their ability to continue to recruit informers rather than to investigate crime.

"I have spoken with the families of the Loughinisland atrocity today and they are bitterly disappointed, heartbroken in fact that the only investigative action arising from the film No Stone Unturned was the arrest of the two people who investigated the matter and sought to expose the truth, rather than to investigate the six murders that occurred and the protection that was afforded to the suspects by police."

Mr Murphy said a High Court challenge by the film company behind the documentary had injuncted the police from examining the evidence seized until the matter was aired at a full court hearing.

Vigil held at Loughinisland, Co Down by the families of those killed in the Loughinisland massacre in solidarity with two arrested journalists, Barry McCaffrey and Trevor Birney (Image: Rebecca Black/PA Wire)

It is understood the custody interviews involved officers from both the PSNI and Durham Police.

Mr McCaffrey walked out of the police station carrying a book about Nelson Mandela.

While the men were held in Belfast, in Loughinisland families and supporters of those killed in the massacre staged a vigil in solidarity with the journalists.

Around 100 turned out to the Heights Bar for the demonstration.

Several held aloft a banner calling for justice for the atrocity and others held framed photographs of their murdered loved ones.

Emma Rogan, whose father was killed in the shootings, said the village was left stunned on Friday morning when they heard about the arrests.

"The whole community were shocked to hear they were arrested while the perpetrators of this heinous act have never been charged," she said.

The attack unfolded on June 18 1994 when loyalist gunmen burst into the Heights Bar and opened fire on customers.

The UVF gunmen struck as football fans watched the Republic of Ireland team play in the 1994 Fifa World Cup.

In 2011, the Police Ombudsman Al Hutchinson found there had been major failings in the police investigation following the shootings, but said there was no evidence that officers had colluded with the UVF.

However in 2016, a new Ombudsman Dr Michael Maguire found there had been collusion, and the police investigation had been undermined by a desire to protect informers.

In 2017, a judge delivered a damning judgment against Dr Maguire's report, ruling that he had exceeded his statutory powers by declaring officers guilty of colluding in the UVF attack.

Another judge is now presiding over a case that will focus on whether Dr Maguire's findings should be formally quashed.